The number of diagnosed cases of diabetes continues to increase in the U.S. and throughout the world, creating enormous economic and public health consequences. Devices and therapies that improve the quality of life for the diabetic patient thus are important not only for the patient, but for society at large. One area in which recently developed technologies have been able to improve the standard of care has been in the maintenance of tight control over the blood glucose levels. It is well known that if a diabetic patient's blood glucose values can be maintained in a relatively narrow and normal range of from about 80 milligrams per deciliter (mg/dL) to about 120 mg/dL, the physiologically damaging consequences of unchecked diabetes can be minimized. With better blood glucose information, diabetic patients can better exercise tight control of their blood glucose level through a variety of means, including diet, exercise, and medication. For this reason a large industry has developed to provide the diabetic population with even more convenient and accurate ways to measure blood glucose. There are many forms of these measuring devices; one common type is represented by hand-held electronic meters which receive blood samples via enzyme-based “test strips”. In using these systems, the patient lances a finger or alternate body site to obtain a blood sample, the strip is inserted into a test strip opening in the meter housing, the sample is applied to the test strip and the electronics in the meter convert a current generated by the enzymatic reaction in the test strip to a blood glucose value.
Some diabetic patients require insulin for the treatment of their diabetes, in order to maintain their glucose levels within the desired range. These “insulin-dependent” diabetic patients have traditionally administered insulin doses to themselves via a hypodermic syringe or with a specialized injector known as an “insulin pen”. Although these injection methods can deliver insulin at an appropriate time and at an appropriate total dosage, the single bolus aspect of the delivery is unlike a physiological profile of insulin production in the body, which involves a lower rate of insulin entry into the bloodstream, over a more extended time course. A more recently available technology is represented by insulin pumps. These devices offer significant therapeutic value as they deliver insulin in a more physiological manner, with measured doses of insulin being infused slowly, over an extended period of time. Further, the rate at which insulin is delivered can be programmed to follow standard or individually-modified protocols, to give the user even better glucose control over the course of a day. Insulin pumps have commercially evolved to become small in size, which offers easier portability and unobtrusiveness, and with electronic advances, they have evolved to become more fully-featured, and thereby capable of enhanced performance. These various advantages in terms of health care quality and user convenience have supported the growth of the insulin pump market.
Diabetics and especially insulin pump users typically carry with them a strip-and-meter glucose test kit at all times, so they can ascertain their blood glucose level during their day. It has been recognized that combining the newer technologies of insulin administration with the newer technologies of glucose measurement could provide user convenience. Such an integrated combination is shown in U.S. Pat. No. 5,665,065, which teaches that the mechanism for measuring blood glucose can be built into the housing of an insulin pump. This patent further teaches that the combined glucose measuring and pump system can permit the user to (1) obtain a glucose value, (2) input the glucose value to the microprocessor based electronics within the pump housing, (3) direct the electronics to calculate a recommended modification to the default or currently in-use insulin delivery protocol, and (4) select either the newly recommended protocol or the original default insulin delivery protocol.
While the advantages of such glucose measuring/insulin pump combinations have been known in the patent literature for many years, in fact, no such device has become commercially available. One fundamental reason for this concept remaining unrealized in the market may involve the now standard and expected watertight feature of the pump, which allows the pump user to shower and swim without removing the pump. On the other hand, waterproofing of a glucose strip testing device is inherently problematic, as the strip port itself is a necessary open connection between the space within the glucose sensing device and the external environment. Thus, the full integration of glucose strip test functionality into an insulin pump would remove the desirable watertight feature of the pump. Such would be the case with a device according to the type shown in U.S. Pat. No. 5,665,065, which if exposed to a wet environment, would allow the entry of water through the test strip opening in the pump housing, where the water could damage the electronics and/or mechanical portions of the pump.
Other practical factors may also contribute to the failure of a combination device to enter the market. Insulin pumps, though expensive, are becoming well established in the market. Pump users tend to remain loyal to their initial choice. Glucose meters, in contrast, are less expensive to acquire (they are often provided to users without charge), and users more often switch between meter brands. Thus, in designing such an integrated combination device, a pump manufacturer would need to commit to particular blood glucose measuring technology in the face of the concern that such technology could become less competitive or even obsolete during the normal life of the pump product. Finally, pump manufacturers are very aware that pump users are interested in pumps that are small and unobtrusive. Clearly, combining two devices can only increase the size of the pump housing, thus making the pump potentially less attractive in a market that has become used to the idea that smaller is better.
In view of these various technical factors associated with the therapeutic devices and the market considerations, it would be desirable to provide an insulin pump user the benefits and performance of a functionally combined glucose measuring device and insulin pump in a configuration that nevertheless avoids the practical disadvantages associated with a physical integration.